The invention relates to a machine tool for machining a rod-shaped workpiece, and, in particular, to a machine tool having a tool spindle and also a first holder and a second holder for accommodating the workpiece.
The invention further relates to a method of machining a rod-shaped workpiece using such a machine tool which has a tool spindle and also a first holder and a second holder for accommodating the workpiece.
A machine tool is known from DE 199 19 647 A1. The known machine tool is a traveling-column machine, on the machine bed of which a workholding fixture for a workpiece is arranged. The workholding fixture is swivelable about a horizontal axis, so that both a longitudinal side and an end face opposite the clamping point of a workpiece clamped therein can be machined by a tool which is accommodated in a tool spindle fastened to the traveling column. In order to also be able to machine the sixth workpiece side, a type of robot arm (manipulator) is provided, this robot arm being swivelable about a vertical axis and having a gripper. After the completion of the machining of the five sides of the workpiece which are accessible first of all, the gripper takes the workpiece out of the workholding fixture. The robot arm is then swiveled by 90° in the horizontal and by 180° about its longitudinal axis and the gripper is put into a clamping station. The clamping station holds and fixes the gripper and thus the workpiece still accommodated therein in a precise position, so that the workpiece can now also be machined on its sixth side by the tool.
In general, conventional lathes also have a workholding fixture with a self-centering chuck, in which the workpiece to be machined is clamped in a rotationally fixed manner. A tailstock, which can be displaced and clamped in place on a machine bed, often serves as the counterpart. In this case, the workpiece is often centered by means of a mandrel which is accommodated in a chuck of the tailstock, this chuck being designed specifically for this purpose and being designated as tailstock quill. Alternatively, or in addition, a steadyrest, for this purpose, is often fastened to the machine bed in a longitudinally displaceable manner in such lathes, this steadyrest supporting the workpiece like an intermediate bearing in order to prevent in this way a deflection of the workpiece under the effect of the cutting pressure.
In order to also be able to machine the workpiece in such lathes at the clamping point at which it is accommodated in the chuck of the workholding fixture, the workpiece is removed from the workholding fixture and clamped again in the latter in a position turned round by 180°. This operation is relatively time-consuming and could hitherto only be automated with difficulty and with considerable design outlay.